Expansion valve



EXPAN S ION VALVE Filed May 5, 1959 3 Sheets-Sheet 1 7 illi igailliififlumndl Ila Manllmesi (Ittomeg Patented Aug. 4, 1942 UNITED STATES2,291,898 nxransren 'vALvE Gifford I1 Holmes, Minneapolis, assignor i toMinneapolis-Honeywell Regulator Company, 7 j/ l AT-ENT orrlctMinneapolis, Minn., a corporation of fieiaware Application May 5, 1939,Serial No. 271,983

18 Claims. (Cl. 62-8) This invention relates to expansion valves andmore particularly to that type of valve known as-thermostatic expansionvalves such as are commonly employed in refrigerating systems.

One of the objects of this invention is the provision of an improvedthermostatic expansion valve of the type which controls the flow ofrefrigerant through the evaporator in a manner to'inaintain therefrigerant at the outlet of the evaporatoLwlmiantiallyconsta .t degreeof superheat.

More specifically it is an object of this invention to provide athermostatic expansion valve and operating means therefor whereby thevalve will control the refrigerant through the evaporator in such amanner that, regardless of variations in temperature and pressure, therefrigerant at the evaporator outlet will be maintained at a'substantially constant degree of superheat, with means for adjusting thesuperheat setting of the valve without affecting the ability of thevalve to maintain the refrigerant at a substantially constant degree ofsuperheat as the temperature and pressure of the refrigerant vary, atthe new superheat setting of the valve.

fication, claims and appended drawings wherein like reference charactersrepresent like parts in the various views and wherein,

Figure 1 is a view of one form of expansion valve and operatingmechanism therefor shown in a conventional refrigeration system,- withcertain parts shown in cross section,

Figure 2 is a modification of the valve and operating mechanism thereforin Figure 1 shown in cross section,-

Figure 3 is a crosssectional view of a still further modification of thevalve and operating mechanism of Figure 1, and

Figures 4 and 5 are views illustrating the temperature pressure curvesof two well known refrigerants.

In the past, expansion valves for controlling the 55 flow of refrigerantthrough an evaporator comprised an operating bellows or diaphragm whichresponded to the temperature of the refrigerant within theevaporatorforcontrolling'the position 5 of thevalve, the operatingbellows ordiaphragm opening the valve upon an increase in'temperature or upon adecrease in pressure. The bellows or diaphragm also responded to thepressure on the suct ign sidepf the system, the pressure being taken atthe inlet oftheevaporator but the valve did not properly respond tomsuperheat of the refrigerant at the evaporator outlet because of thepressure drop existing within the evaporator, particularly on systemsusing a relatively large or multiple coil type of evaporator, thepressure drop being variable depending upon the load on the evaporator,so in order to make the valve properly respond to the superheat at theevaporator outlet a connection known as an equalizer connection wasprovided between the outlet of the evaporator and the operating bellowsor diaphragm so that the bellows or diaphragm properly responded to thepressure at the evaporator outlet. This arrangement while satisfactorily'controlling the valve according to the superheat at the'evaporatoroutlet, did not act to maintain the superheat at a fixed value as thetemperature and pressure of the refrigerant leaving the evaporatorvaried, so that the efiective cooling area of the evaporator, or thatportion thereof which was in a flooded condition would varyflastlre'temperature and pressure of the refrigerant leaving the evaporatorvaried.

Upon reference to Figure 4 it will be seen why such valves would notproperly maintain the superheat of the refrigerant leaving theevaporator at a constantvalue. ,Curve A shows the pressure temperaturecurve for the refrigerant Freon or F-12. It will benoted that this curve40 is not a straight line. Curves for all known rerange is about 3 lbs.per square inch. On the other hand, as the temperature of therefrigerant increases from 20 F. to 30 F. the pressure corresponding tothis temperature increases from approximately 36 lbs. to 44 lbs. persquare inch; or in other words, for this 10 rise in temperature thepressure increases by approximately 8 lbs. In the conventionalthermostatic expansion valve a spring is employed which opposes theaction of the power or operating bellows or diaphragm; or in otherwords, tends to close the valve agaih'st thep ning force exerted thereondue to a rise in armature. These springs generally exert asubstantiamonstant force upon the valve and may be adjusted maintain acertain degree of superheat of the 1 refrigerant at a given value oftemperature, for example: Assume that it is desired to maintain asuperheat of the 55mm W .orator outlet when the suction pressure 1535'lbs. The temperature of the saturated refrigerant corresponding to thispressure will be approximately 18 F. as will be noted from curve A ofFigure 4. If the refrigerant is to be maintained at a 10 superheat thetemperature of the refrigerant should be 28 and the pressurecorresponding to this Emperature wiilbeapproximatelMii-lbsfifi'ccordingly the spring which.

3 o! Figure 5. In va ves ei3 ploying operating bellows ordiaphragms.havingdiiferentsizedareas asshown in the Newton applicationhereinbe- 1 fore identified, if the force exerfiddiy the spring isincreased, the superheat line in Figur e5\ wouldbe above the line D ofFigure 4 but since the spring rate would be the same as before thesuperheat line would be parallel with the line D of Figure 5 and if thisline were transposed onto Figure 4 it would illustrate that the valve,would notmaintain the superheat at a constant "value for varyingpressures and temperatures. equal to the difference of the 35 lbs.suction prese a ou t t a t e superheat would y from sure and the 43 lbs.pressure which corresponds the s d v ue would in e as t e Sp to thepressure of the saturated'refrigerantsatihew was adjusted from theproper settin o whlai higher temperaturef'of in other words, a forcemodelled. H wev r 1 the n l uequaktvSlbs. As the temperature graduallyloading of e Spring and e pr ng ate are decreases at the outlet of theevaporator the h p perly Va ied he valve will maintain the superheatwill gradually increase as explained superheat v ,if superheatis d ralon below. Assume that the pressurev at the outlet the line F. This isone of the features of the of the evaporator drops to 20 lbs., thetemperapresent invention. Thus, increasing h sp i ture of the saturatedrefrigerant at this pressure loading ld move the line Figure upwill beapproximately -7 F. and if the spring d y pa a w t se a d increasing thecontinues to exert an 8 lb. closing force the pres- Spring rate ou d c ehe inclination of the sure corresponding to the temperature of the line,so that by properly s e' e Spring e refrigerant 111 be approximately 2and for 20 superheat, the inclination and position the temperature ofsaturated refrigerant correwould be changed to t of ne F. Theremainsponding to 28 lbs. pressure is approximately 8 ing full n curvesof Figure 4 illustrate the opposes the opening of the valve exerts aforce F. Thus the superheat of the refrigerant leaving the evaporator atthis lower pressure will so that while the evaporator is operetih'get'a" lower temperature, the effective cooling surface thereof hasdecreased.

The curve B shows the constant 10 superheat r curve and the verticaldistance W between the curves A and B shows the actual closing forcethat should be exerted on the valve at varying temperatures andpressures in order that the superand superheat curves, which curves alsoappear as straight lines in Figure 5, but these lines have increasinginclinations as the amount of superheat increases. Similar curves forthe refrigerant ammonia are illustrated by dotted lines,

the saturated ammonia curve of Figure 4 coincidin'g with the line C ofFigure 5. In this figheat existing at the outlet of the evaporator willK together in conventional ma er. The valve [3 at-all times be constant.This curve Bit willbe i 209F the flow of e ant through the evapnoted hasa curvature somewhat similar to the islalv is Shown to mpr e a curve Abut gradually diverging therefrom as the Casing comp se of a lower'secton 20 and en temperature increases and if. the ourveAbetaken upper t onhe section 20 includes an as the base line,'as shown by the line C ofFiget p g 2 through which high P essur ure 5, and the curve B plottedfrom this line; as C f i eran flowsand the outlet openin II conshown bythe line D of Figure 5, it will be seen trolled by the valve element 24.This valve elethat the line D is also a straight line. In order" mentmay be Su ly Supported within the for the valve to operate along theline D of Figs s ti n 20 and is shown to be connected to ure 5 which isthe constant 10 superheat line, one end of a lever 25 pivoted at 25 dhaving the areas of the bellows or diaphragm which the opposite endengaged by the compression responds to the temperature of therefrigerant Sp 21 w ich acts to as t e valve towards may be madeslightly smaller than the area of closed position. The position of thelever 25 is the bellows or diaphragm responding to the prest olled by te pl er 30 Suitably o ected sure, as disclosed in the application SerialNo. to the bellows 3| mounted in the upper casing 192,818 filed by A. B.Newton on February 26. section 2|. Apartition 32 separates the two por-1938. By choosing the proper relative sizes of tions of the casing andthis partition has an the bellows or diaphragms responding topresopening 33 through which the plunger 30 ex sure and temperature andby choosing the proptends. there being a suitable sealing bellows 34 orspring to bias the valve towards closed posifor preventing escape ofrefrigerant into the upper portion 2| of the casing. A spring 35 opposesthe expansion of the. bellows 3| and tends to permit closing of thevalve under the influence of the spring 21. r

The bellows 3| is in communication by means of the capillary tube 38with a bulb 39 located within the evaporator outlet, this bulb 39havingan expansible portion in the form of a bellows 40 for a purpose to bedescribed; The portion of the evaporator within which the bulb 39 ismounted has an enlarged portion 4| which forms a chamber for thediaphragm 42 which may be suitably clamped between the enlarged portion4| and the cover member 43 by means of the bolts 44. The diaphragm 42 issealed to the lower portion of the bellows 49' and this diaphragm isnormally biased upwardly by means. of the compression spring 45 heldbetweeri'the spring retainer 46 fastenedto the lower portion of thediaphragm and the recessed adjusting screw 50 which is adjustablyreceived by the cover member 43. g a r As the pressure of therefrigerant-leaving the evaporator increases, the diaphragm 42 will beforced downwardly against the force of the spring 45 and this movementof the diaphragm will cause an expansion of the bellows 40 forming thelower end of the bulb 39 which will have the effect of increasing thevolume of this bulb. The bulb 39, tube 38, and bellows 3| may beprovided with a suitable liquid fill which will have a substantiallyconstant volume as long as the temting of the spring'45, that is,-agiven loading and spring rate, the valve 24 will move in a manner tomaintain a constant superheat at the outlet thereof. Thus with the partsadjusted as shown in'the drawings it"may be assumed that the valve isadjusted to maintain. a superheat of using the refrigerant F-12 so thatthe valve will'control the refrigerant. according to the curve B ofFigure 4 or curve D of Figure 5.

The adjusting screw 50 is for the'purpose of adjusting the initialloading of thespring' and this screw may be providedwith a suitablepointer 54 which maycooperate with suitable indicia away from thediaphragm 42 without changing the force .of the spring 45 but byincreasing or on the cover 43. d V screw 50 is an adjustingscrew 55having suitable stop rnernbers 56 which serve. as abutment members forthose coils of the spring which are located between the members and thediaphragm 42. By reason of the adjustment of the screw 55, the abutmentmembers 55 move towards or ingly if it is desired to increase thesuperheat setting of the valve from 10? to 20, for example,

perature at the bulb 39 remains constant, so I that as the volume of thebulb 39 increases, the bellows 3| will collapse by an amountcorresponding to the increase in volume of the bulb. This action of thebellows 3| will permit the valve 24 to move towards closed positionunder the influence of the spring 21, thereby reducing the flow ofrefrigerant into the evaporator and causing a reduction in pressuretherein. On the other hand, if the pressure of the refrigerant shoulddecrease at the evaporator outlet, diaphragm 42 will move upwardly,collapsing bellows 40 which reduces the volume of bulb 39, and bellows3| will expand a corresponding amount, thus causing an opening movementof valve 24, which increases the flow of refrigerant into theevaporator. It will thus be seen that the fill in the bulb, tube, andbellows acts as a hydraulic transmission means to transmit movements ofthe diaphragm 42 into movements of the bellows 3|.

If now the temperature of the refrigerant leaving the evaporator shouldincrease, there will be an expansion of the liquid fill in the bulb 39which will cause an expansion of the bellows 3| and an opening. movementof the expansion valve. Conversely, upon a decrease in temperature ofthe refrigerant leaving the evaporator, the volume of the liquid withinthe bulb 39 decreases, whereupon the bellows 3| will collapse inaccordance with this decrease in volume, and the valve 24 will movetowards closed position under the influence of spring '21, thus reducingthe flow of refrigerant to the evaporator. It should be noted that thearea of the diaphragm 42 which responds to the pressure of therefrigerant leaving the evaporator is considerably larger than the areaof the bellows 3.l which responds directly to the temperature of therefrigerant and also moves in accordance with the change in pressure byreason of the expansion or contraction of the bellows 40 and theserelafive areas will be so chosen that for a given setthe adjusting screw50 will be turned until the indicator 54 has moved to the proper.position wherein the loading of the spring 45 has been increased theproper amount. The adjusting screw 55 will also be adjusted until theindi-' cator has moved to the position corresponding to the adjustmentof the member 50 whereupon the spring rate has been increased the properamount and the valve is now properly adjusted to maintain therefrigerant leaving the evaporator at a constant degree of superheat,namely, 20 F. regardless of normal fluctuations in temperature andpressure. By adjusting the spring rate of the spring, the line D wastilted upwardly until it was parallel-with the line F.

and the change in the spring loading moved the line upwardly until itcoincided with the line P, which line corresponds to the 20constant'suprheat line E of Figure 4.

In the conventional type of expansion valve, employing a diaphragmresponding to the superheat at the evaporator outlet, directly connectedto the valve element, and having a spring opposing movement of thediaphragm in valve opening direction, the valve element will assume apredetermined position for each position of the diaphragm. In such anarrangement, if the spring rate of the spring were adjusted, the onlyeffect upon the operation of the valve would be to change the operatingdifferential thereof. A change in the loading of the spring would changethe amount of superheat that would be maintained for a given pressure ofthe refrigerant at the evaporator outlet, since, again referring toFigure 5, the line D would be moved upwardly but since the line couldnot be made to coincide with the line F, the valve would not maintainthe superheat constant for varying temperatures and pressures at theevaporator outlet.

In my arrangement, the diaphragm move in response to variations inpressurefof the refrigerant leavingthe evaporator outlet, but variationsin temperature of the refrigerant at the Threadedly received by theposition of. the diaphragm and the valve position by reason of thenature of the connections between the diaphragm and the valve element,and

this: isnan important feature of this invention which 'cofiti'ibutestothe new result which is obtained thereby. FOr' any position of thediaphragm, the valve position willdepend upon the temperatureoftherefrigerant leaving the evaporator. The positioii'of"the'diaphragmdepends upon the-pressure of the refrigerantleavin the evaporator.diaphragm for any refrigerant pressure depends upon the spring loadingand the spring rate which, if properly adjusted, will cause the valve tomaintain any desired degree of superheat, and maintain the superheatsubstantially constant for varying outlet pressures and temperatures.

With this form of valve therefore it will be apparent that it may be setfor different degrees of superheat by adjusting the loading and springrate of the spring 45, and will maintain the superheat constant forvarying degrees of pressure and temperature. By placing the diaphragm 42at the valve outlet the necessity of using the usual equalizerconnection is obviated and th only connection between the valve and theevaporator outlet which is required is the tube 38.. This arrangement ismade possible since the pressure responsive diaphragm 42 does not actdownwardly upon the valve but acts merely to adjust the volume of thebulb 99 which in turn varies the expansion of th operating bellows 3|.It should be understood that any suitable control means for therefrigerating apparatus may be provided. Referring to Figure 2, thevalve and operating mechanism herein illustrated are formed as a unitarystructure as distinguished from the apparatus shown in Figure 1 in whichthe bulb and pressure responsive diaphragm are formed as a unit separatefrom the expansion valve itself. In, this form of the invention thevalve is shown to be made of a plurality of sections 10, H, 12, and 13.The section includes the inlet opening H and the outlet opening 15, thevalve element 16 carried by the lever 11 and pivoted at "cooperatingwith the opening I5, the valve being biased towards closed position bymeans of the spring 19. Clamped between the sections II and 12 is adiaphragm 89, the sections II and 12 being suitably recessedasillustrated to permit movement of the diaphragm with respect to thesesections and to form a pressure chamber Furthermore, the position of te15 above the diaphragm. Connected to the dia- I phragm is the plunger8| extending through the opening 82 in the section II, this plungeracting on the lever 11 so that as the diaphragm 80 moves downwardly themovement thereof is transmitted by the plunger 8| to the lever 11 tomove'the valve element towards open position. The space within thesection III is sealed from the diaphragm by means of the bellows 83connected to the plunger 8|. The upper portion of the diaphragmcommunicates by means of the passageway 84 with the capillary tube 85connected to a bulb 86 whichis subjected to the temperature of therefrigerant in the outlet of/ the evaporator, this bulb and tube beingprovided with a suitable fill which may be a volatile or liquid fillso'that as the temperatur or the refrigerant leaving the evaporatorincreases, ari

diaphragm 90, the under portion of which ,has'

connected thereto a bellows 9| sealed to the section 12, as illustrated.The space between the diaphragm 90 and the section 12 formed byrecessing the upper portion of this section is placed in communicationwith the outlet of the evaporator by means of the port 94 and the tube95. The tubes 85 and 95 may be concentrically arranged as illustratedsothat the bulb 86 may be mounted within the evaporator outlet to moreaccurately respond to the temperature of the refrigerant leaving theevaporator as disclosed in the above"rrientioned Newton application.'I'hediaphragms 80 and 99 are suitably connected together by a tensionspring 96 so that if th diaphragm 9,9 is moved upwardly by reason of anincreasein pressur at the evaporator outletthe tension of the spring 96will be increased and will cause the diaphragm 80 to move in the samedirection thuspermitting movement of the valve 11 towards closedposition. The upward movement of the diaphragm 90 is opposed by means ofa compression spring I00 with which cooperates adjusting screws l0! andI02 for adjusting the loading and spring rate of the spring asillustrated in Figure 1.

It will be noted that the area of the diaphragm 90 is larger than thatof the diaphragm 80 which moves directly in accordance with thetemperature of the refrigerant leaving the evaporator and whilethebellows 9| reduces the effective area of the diaphragm 90 it reducesby the same amount the effective area of the diaphragm 80 and the areasof the two diaphragms will be so chosen that with the proper adjustmentsof the spring I00 the superheat of the refrigerant leaving theevaporator will be maintained at the desired value. The diaphragm 90, itshould be noted, doesnot directly control the position of the valve 11.but when used with a volatile fill in the bulb 88, acts merely to adjustthe tension of the spring 96 which exerts a closing force on the valveso that when the pressure of the refrigerant increases, the tension ofthis spring is increased and thediaphragm 80 will move upwardly thusin-, creasing the'closing force exerted on the valve by the spring 19.Similarly upon a decrease in pressure the downward movement of thediaphragm will reduce the force exerted by the spring 96 and thediaphragm 80 will move downwardly so that a smaller force must beexerted on the diaphragm 80 to open the valve. However, when a liquidfill is used in the bulb 86 and the chamber above the diaphragm 80, thespring 96 can be omitted without substantially affecting the properoperation of the valve 16 because a liquid will tend to remain at aconstant volume without the assistance of a spring.

Refrigerant enters the opening Il3 in the upper I 4 section of the valvecasing and passes through the opening I I2 and outwardly from the valveby wayof the opening Ill which is controlled by the valve element 16.The lower end of the bellows H is connected to a plate member II6 whichmoves with the bellows and which receives the compression spring I"having the adjustable abutment H8 threadedly received within the closuremember I20 in the lower wall of the valve casing. The bellows III! issealed to the lower wall of the casing by means of the sealing bellowsI2I. Carried by the periphery of the plate member H6 are pins I22, onlyone of whichis illustrated, which bear against the free arms of thelever 11 which may be in the form of a yoke, and downward movement ofthe plate member by reason of an increase in pressure within the bellowsIII! will cause an upward or opening movement of the valve element 16against the force of the closing spring 19.

Sealed to the upper wall of the partition I II is a bellows I25 havingits upper end connected to the plate member I26 which is in turn sealedby means of the bellows I21 to the closure member I28. The interior ofthis bellows is in pressure responsive communication with the outlet ofthe evaporator by means'of the pipe 95 and-the passageway 94. The platemembers H6 and I26 connected to the bellows H0 and I25, respectively,are connected 'to a tensionspring I35 which tends to maintain thebellows H0 and I25 in a collapsed condition. This spring passes throughthe opening H6 in the center of the partition III and a sealing bellowsI31 seals the interior of the bellows I25 from this opening so that thebellows H0 and I25 are properly sealed from one another. a p

The plate member I26 is biased downwardly by means of the spring I06having adjusting means IGI and I62 similar to that shown in Figure 2.The bellows I Ill and I25 will be kept in a warm condition at all timessince they are surrounded by high pressure refrigerant entering theinlet H3 as is apparent from the drawings. The seal-off bellows I2! andI21 prevent the pressure of the high pressure refrigerant fromefiecting' the operation of bellows H0 and I25, respectively. I Theoperation of this .valve is substantially the same as that of Figure 2since an increase in pressure will cause expansion of the bellows I25desired values of superheat of the refrigerant at the evaporator outletwill be maintained constant load conditions.

low that the force of the spring 19 in Figure 2 or the springs 19 and III in Figure 3 is not overcome the valves will remain in closedpositions. A certain amount of force is of course required to overcomesprings 19 and Ill and the evaporator temperature may drop so low thatthe required force on diaphragm 80 or bellows I'IO may not be developedand the valves will remain closed.

7 This will normally happen only when the load thereon becomes verylight. When this happens however the temperature of the refrigerantleaving the evaporator may drop below a certain value whereupon thevalves will close entirely and will not open again until thistemperature has risen above this value. Before this happens however thepressure within the evaporator will continue to drop so that thesuperheat at this time at the outlet of the evaporator will increase andthe evaporator coil will gradually become more and more starved. Theratio of latent cooling to sensible cooling will thus increase by reasonof the diminishing eflective coil area and the simultaneous reduction inpressure in the evaporator which is very desirable under light Thespring II! in Figure 3 is made adjustable so that the temperature atwhich the-valve is closed regardless of the pressure may be adjustedaccording to the requirements of the system. It should of course beunderstood that the spring 19 of Figure 2 may, if desired, also be madeadjustable for the same purpose.

It will accordingly be seen that .the valves of Figures 2 and 3, besidesoperating to maintain constant any desired degree of superheat over anormal operating range, also operate to prevent 'the flow of refrigerantto the evaporator whenever the temperature of the refrigerant at theoutlet'thereof drops below a predetermined value. This is made possibleby reason of the novel arrangement of the operating bellows ordiaphragms, the one responding to the pressure of the refrigerant notbeing directly connected to the valve but merely acting upon a tensionpressure.

regardless of normal fluctuations in temperature and pressure.

In both Figures 2 and 3, if the temperature of the refrigerant at theevaporator outlet' should become sufiiciently low, the diaphragm 80 orbellows III) will not exert sufiicient force to open the valve againstthe closing force exerted by the spring 19 in Figure 2, or the springs1.9 and III in Figure 3, regardless of how low the pressure becomes. Inother words, these springs 96 and I35 connecting the operating bellowsor diaphragms may exert no force whateverbecause the pressure of therefrigerant has dropped so low, but if the temperature has also droppedso Having described some preferred forms of my invention it will beobvious that many m'odifications will become apparent to those skilledin the art and I therefore wish it to be understood that my invention islimited only by the scope of the appended claims.

I claim as my invention:

1. In a refrigeration system, an evaporator, valve means for controllingthe flow of refrigerant through said evaporator, means responsive to apressure corresponding to the temperature of the refrigerant at theevaporator outlet for adjusting the position of said valve means, meansresponsive to the pressure of the refrigerant at the outlet of theevaporator for modifying said first responsive means'in a manner tomaintain the refrigerant leaving the evaporator.

at a substantially constant degree of superheat as the temperature andpressure of the refrigfor modifying the action of one of said last namedmeans in a manner to cause the valve to maintain a differentsubstantially constant degree of superheat of the refrigerant at theevaporator outlet for varying temperatures and pressures of therefrigerant at the outlet.

2. In a refrigeration system, an evaporator, valve means for controllingthe flow of refrigerant through said evaporator, means responsive to thetemperature of the refrigerant leaving the evaporator controlling theposition of said valve means, means responsive to the pressure of therefrigerant on the suction side of the system for modifying the effectof the temperature responsive means, spring means cooperating with thepressure responsive means, means for adjusting the loading and springrate of said spring means, to' cause the refrigerant at the evaporatoroutlet to be maintained at a substantially constant de gree of superheatwhich varies in accordance with the spring rate and loading on saidspring means but which does not varyappreciably with normal changes oftemperature or pressure of the refrigerant at the evaporator outlet.

3. In a refrigeration system, an evaporator, valve means for controllingthe flow of refrigerant through said evaporator, means responsive to thetemperature of the refrigerant leaving the evaporator controlling theposition of said valve means, means responsive to the pressure of therefrigerant on thesuction side of the system for modifying the effect ofthe temperature responsive means, spring means cooperating with thepressure responsive means, means for adjusting the loading and springrate of said spring means, to cause the refrigerant at the evaporatoroutletto be maintained at a sub- "erant leaving the evaporator vary, andmeans movement of said valve means upon a rise in pressure occasioned bya rise in temperature at said bulb, means responsive to the pressure ofthe refrigerant at the evaporator outlet for varying j the volume ofsaid bulb to vary the effect of the a rator outlet.

6. In a refrigeration system, an evaporator, valve means for-controllingthe fiow of refrigerant through the evaporator, pressure responsivemeans for controlling the position of said valve means, a fiuid filledexpansible and contractible bulb responsive to the temperature of therefrigerant leaving the evaporator in communication with said pressureresponsive means,

said pressure responsive means causing opening movement of said valvemeans upon a rise in pressure occasioned by a rise in temperature atsaid bulb, means responsive to the pressure of the refrigerant at theevaporator outlet for varying the volume of said bulb to vary the effectof the temperature of the refrigerant leaving the evaporator on theposition of said valve means,

stantially constant degree of superheat which varies in accordance withthe spring rate and loading on said spring means but which does not varyappreciably with normal changes of temperature or pressure of therefrigerant at the evaporator outlet, and means urging the valve inclosing direction for preventing opening of the valve means whenever thetemperature of the refrigerant at the evaporator outlet drops to apredetermined value irrespective of the pressure of the refrigerant atthe evaporator outlet.

4. In a refrigeration system, an evaporator, valve means for controllingthe flow of refrigerant through the evaporator, pressure responsivemeans for controlling the position of said valve means, a fluidfilledexpansible and contractible bulb responsive to the temperature ofthe refrigerant leaving the evaporator in communication with saidpressure responsive means,

pressure occasioned by a rise in temperature at said bulb, and meansresponsive to the pressure of the refrigerant at the evaporator outletfor varying the volume of said bulb to vary the effect of thetemperature of the refrigerant leaving the evaporator on the position ofsaid valve means.

5. In a refrigeration system, an evaporator, valve means for controllingthe flow of refrigerant through the evaporator, pressure responsivemeans for controlling the position of said valve means, a fluid filledexpansible and contractible bulb responsive to the temperature of therefrigerant leaving the-evaporator in communication with said pressureresponsive means, said pressure responsivemeans causing opening andmeans controlling the change in volume of refrigerant at the evaporatoroutlet in a manner to maintain the superheat of the refrigerant leavingthe evaporator at a substantially constant value regardless of normalvariations in the pressure or temperature of the refrigerant at theevaporator outlet, said last named means including a spring and meansfor individually adjusting'both the loading and spring rate of saidpring.

'7. In a refrigeration system, an evaporator, I

being located within the outletof the evaporator whereby it is subjectedto the temperature of the refrigerant leaving the evaporator, said bulbbeing in communication with an expansible bellows, means responsive tothe pressure in the outlet of the evaporator sealing said bellows andarranged to cause the expansion of said bellows upon a rise in pressurein the evaporator outlet, and biasing meansopposing movement of saidlast named pressure responsive means.

8. In a refrigeration system, an evaporator, valve means for controllingthe flow of refrigerant through the evaporator, operating means forcontrolling the position of said valve means, said operating meansincluding a first pressure responsive means operatively connected tosaid valve means, a second pressure responsive means, resilient meansconnecting said pressure responsive means and biasing the same towardsone another, and means subjecting the adjacent portions of the pressureresponsive means respectively to a, pressure corresponding tov thetemperature of the refrigerant at the evaporator outlet and to thepressure on the suction side of valve means for controlling the flow ofrefrigerant through the evaporator, operating means for controlling theposition of said valve means,

' of said spring means, and additional means for said operating meansincluding a first pressure responsive means operatively connected tosaid valve means, a second pressure responsive means, resilient meansconnecting said pressure responsive means and biasing the same towardsone another, means subjecting the adjacent portions of the pressureresponsive means respectively to a pressure corresponding to thetemperature of the refrigerant at the evaporator outlet and to thepressure on the suction side of the refrigeration system, additionalsprings means for biasing the second temperature responsive meanstowards the first pressure responsive means, and means for varying theloading and the spring rate of said springs means.

10. In a refrigeration system, an evaporator, valve means forcontrolling the flow of refrigerant through the evaporator, operatingmeans for controlling the position of said valve means, said operatingmeans including a pair of adjacent substantially parallelly arranged,diaphragms, means sealing the adjacent faces of said diaphragms fromone another, resilient means connecting said diaphragms and biasing thesame towards one another, one of said diaphragms being connected to saidvalve means, means subjecting the inner face of said one diaphragm to a,pressure corresponding to the temperature of the refrigerant at theoutlet of the evaporator, and means subjecting the inner face" of theother diaphragm to the pressure on the suction side of the refrigerationsystem.

11. In a refrigeration system, an evaporator, valve means forcontrolling the flow of refrig-' erant through the evaporator, operatingmeans for controlling the position of said valve means,

evaporator, means urging the movable portion of said bellows in a valveclosing direction, said means including a member movable in response tovariations in pressure on the suction side of the refrigeration systemand means comprising a tension spring connecting said member to themovable portion of said bellowsQ 12. In a refrigeration system, anevaporator, valve means for controlling'the flow of refrigerant throughthe evaporator, operating means for controlling the position of saidvalve means, said operating means including a bellows having a movableportion operatively connected to said valve, means subjecting theinterior of said bellows to a pressure corresponding to the temperatureof the refrigerant at the outlet of the adjusting the loading of saidspring means.

13. In a refrigeration system, an evaporator, valve means forcontrolling the flow ofrefrigerant through the evaporator, means formingan expansible chamber having a pair of movable wall portions, tensionmeans urging said wall portions towards one another, means operativelyconnecting one of said wall portions to the valve means, meanssubjecting the interior of said chamber to a pressure corresponding tothe temperature of the refrigerant at the evaporator wall portions,tension means urging said wall portions towards one another, meansoperatively connecting one of said wall portions to the valve means,means subjecting the interior of said chamber to a pressurecorresponding to the temperature of the refrigerant at the evaporatoroutlet, means urging said other wall portion in a direction to increasethe tension of said tension means 'in response to an increase inpressure on the suction side of the refrigeration system, and adjustablespring means urging said second wall portion in a direction to decreasethe tension of said tension means.

15. In a refrigeration system, an evaporator, valve means forcontrolling the flow of refrigerant through the evaporator, an operatingmember for said valve means, means responsive to the pressure of therefrigerant on the suction side of the refrigeration system, hydraulicforce transmitting means for transmitting movements of said pressureresponsive means to said valve means, said hydraulic force transmittingmeans including an expansible fluid, a portion of said expansible fluidbeing subjected to the temperature of the refrigerant leaving theevaporator whereby said valve means also moves in responseto variationsin temperature of the refrigerant at the evaporator outlet. v

16. In a refrigerating system, an evaporator, valve means forcontrolling the flow ,of refrigerant through said evaporator, meansresponsive to the pressure and temperature of the refrigerant leavingthe evaporator for controlling the valve to maintain the refrigerantleaving the evaporator at a substantially constant degree of superheat,said last means embodying means for compensating for variations inevaporator pressure so that the degree of superheat remains constanteven though the evaporator pressure varies, means for adjusting thesecond mentioned means for varying the degree of superheat to bemaintained by adjusting the responsiveness of said responsive means,said adjusting means embodying secondary adjusting means cooperatingwith said compensating means whereby variations in evaporator pressureare compensated for at the adjusted value of superheat so that degree ofsuperheat may be maintained constant at selected values irrespective ofevaporator pressure.

17. In a refrigerating system, an evaporator, valve means forcontrolling the flow of refrigerant through said evaporator, meansresponsive to the pressure and temperature of the refrig valve tomaintain the refrigerant leaving the evaporator at a substantiallyconstant degree of superheat, said last means embodying means forcompensating for variations in evaporator pressure so that the degree ofsuperheat remains constant even though the evaporator pressure varies,means for adjusting second mentioned means for varying the degree ofsuperheat to be maintained by adjusting the responsiveness of saidresponsive means, said adjusting means emvalve means including apressure chamber having a movable Wall portion, means communicatingevaporator pressure to said chamber urging said wall portion in onedirection, means forming a second pressure chamber having a movable wallportion, means producing a pressure in said last chamber correspondingto the temperature of refrigerant at the outlet of the evaporator,resilient means opposing movement of one of said wall portions,yieldable means interposed between said movable wall portions and avalve member connected to one of said wall portions adapted to assume aposition depending on both wall portions, and said resilient meanscomprising a spring having manual means for adjusting both its loadingand spring rate,the valve means being arranged to maintain a constantnumber of degrees of superheat at the outlet of the evaporator eventhough the evaporator pressure varies, the number of degrees ofsuperheat depending on the adjustments of said manual means.

GIFFORD I. HOLMES.

